1. Field of the Invention
This invention relates to and teaches processes for making reformed or well-graded fiber made from waste carpet materials. The invention further teaches the use of such fibers for improving cementitous structures such as concrete roadbeds and concrete beams, piers, statuary and other cementitous structural elements. The invention also discloses processes for employing the reformed fibers for improving the static and dynamic physical properties of structural entities such as hot-mix asphalt roadbeds. The invention further teaches the use of well-graded fibers for reinforcing other congealable materials including plastics and glues and laminates employing one or both.
Effect of Waste Carpet on the Environment:
Thousands of tons of carpeting are annually removed from offices and homes and discarded in landfills. Many of these carpets are fabricated from man-made fibers such as Nylon (TM Dupont Co.), polypropylene and similar materials. These materials are not biodegradable and therefore never decay or undergo any of the biological degradation processes. Further, the carpeting sheds water and thereby prevents water from reaching and decaying degradable materials underneath.
Economics
The beneficial use of waste carpet instead of disposal in landfill provides an immediate important economic benefit. Other benefits arise from improvements in the static and dynamic physical properties of structural, construction and road surfacing materials. These economic benefits are related to the longer life of the products and the road surfaces arising from their improved resistance to cracking, the reduced annual costs for maintenance and replacement and the avoidance of economic loss arising from replacement and other costs that occur during the periods required for repair and replacement. Cementitous structures employing reformed or well-graded fibers can have lighter weight and thinner sections that use less Portland cement. Further, Portland cement production is a significant contributor to atmospheric carbon dioxide pollution. By contrast, such structures formed from prior art fibers that are of substantially uniform length (gap-graded) impart significantly less improvement in physical properties. Glue bound laminates formed with well-graded fibers have higher moduli and therefore are stiffer and require thinner sections or can offer longer spans. Typical congealable glues are cyanoacrylates, epoxies, heat or ultra violet curables, hot melt types, foams and various industrial adhesives
2. Prior Art
The use of high quality fibers, such as Nylon™, for reinforcing cementitous or asphaltic structures has been limited for three reasons. First has been the relatively high cost of Nylon. Virgin Nylon fiber in 2005 costs about $1.00 per pound. Second is the difficulty of handling, feeding and mixing loose, virgin fibers into either hot asphalt liquid or into cementitous mix prior to their application. Third is the fact that physical property improvements imparted to the hot-mix asphalt or cementitous structural materials which result from the use of high quality fibers that are similar in length has been disappointingly small.
Asphalt Current Usage
A typical road construction product of hot-mix asphalt has about 93% aggregate of stones, sand and recycled waste materials. Typically six percent (6%) by weight of the final mixture is the liquid asphalt binder. Where fibers are specified, polyester is used at the rate of 6 pounds fiber per ton of total mix or 5% by weight of the liquid asphalt. Polyester fiber is supplied in bags as a pre-weighed, loose, fluffy bulk material.
One manufacturer has developed a process for recycling the material in waste carpets by ‘ginning’ the carpet fibers. His process produces so-called “gap-graded” fibers that are substantially the same length. The fibers so produced are curly and feed poorly into processes. To improve feeding and flow of the fibers, the manufacturer reassembles the extracted Nylon fibers in small pellets bound together by the polypropylene carpet component. These pellets have been used to add fiber to asphaltic compositions by virtue of the ease with which the pellets can be measured and fed into the mix. Also, while this process incurs an expense, the resulting pellets are considered suitable landfill material since the pellets do not impede moisture flow within the landfill, even though the pellets themselves do not biologically degrade. Further, the calcium carbonate backing material is lost and discarded.
Concrete Current Usage:
A typical road, cast statuary, building beams or other structural element or foundation employing Portland cement concrete has about 85% aggregate of stones and sand with only about 15% of the concrete mix being the Portland cement or other cementitous binder and water. Steel and other fiber binders have been experimentally used in Portland cement concrete and other cementitous products to improve their physical properties. Typical fiber concentrations that have been employed in fiber reinforced concretes range from 2 to 5 pounds polyester or polyolefin fiber per cubic yard finished concrete.
Fiber binders are known to have been used in thermally or chemically hardening materials to improve their strength, flexibility and resistance to cracking. The State of Ohio publishes Standard #400HS titled, “Standard Specification for Asphalt Concrete—High Stress using Polypropylene Fibers.” The use of fiber bearing Acrylic Fill for coating tennis courts is promoted by Vance Brothers, Inc. of Kansas City, Mo. 3M has published an advertising piece reporting on the use of its polyolefin fibers as reinforcement in Portland cement concrete installed on a stretch of U.S. Highway #83 bridge structure over highway I-90 South of Pierre, S. Dak. No method for applying the fibers is taught.
U.S. Pat. No. 5,028,266 by Stephen Rettenmaier teaches the use of ‘granulates’ comprising cellulose fibers held together by bitumen or other petroleum product that dissolve in hot petroleum asphalt. A mix of equal weights of the fibers and the bitumen are extruded and chopped into lengths or granules. Rettenmaier relies on the heat and solvent action of the hot asphalt to disrupt his granules. Rettenmaier does not teach the use of his ‘granulates’ in Portland cement concrete.
Waste Nylon carpets have been a potential resource for reinforcing fibers since the carpets contain about 50% Nylon fiber, 10% polypropylene used in the backing along with styrene-butadiene polymer and calcium carbonate.
Prior carpet reclaiming processes yielded a fluffy, curly, twisted fiber that was primarily gap-graded, is difficult to handle, difficult to dispense reliably and accurately and subsequently provided disappointing reinforcement value.